I suggest that you tour Michigan first, including driving through the Upper Peninsula and down into Wisconsin. Then get a feel if you still want to do Chicago or even have the time for it.
It would be ideal if you could find a park by public transportation so you don't have to drive into Chicago. Also, at least the first day, take a small van tour of the city. Those kinds of tours really give you the highlights and you can then get your bearings as to where things are if you want to go alone on future days. We loved doing San Francisco that way. Trying to see a big city in a day or two on your own is usually wasted time.